1. Field of Inventions
The present inventions relate generally to structures for positioning diagnostic and therapeutic elements within the body and, more particularly, to devices which are particularly well suited for the treatment of cardiac conditions.
2. Description of the Related Art
There are many instances where diagnostic and therapeutic elements must be inserted into the body. One instance involves the treatment of cardiac conditions such as atrial fibrillation and atrial flutter which lead to an unpleasant, irregular heart beat, called arrhythmia.
Normal sinus rhythm of the heart begins with the sinoatrial node (or xe2x80x9cSA nodexe2x80x9d) generating an electrical impulse. The impulse usually propagates uniformly across the right and left atria and the atrial septum to the atrioventricular node (or xe2x80x9cAV nodexe2x80x9d). This propagation causes the atria to contract in an organized way to transport blood from the atria to the ventricles, and to provide timed stimulation of the ventricles. The AV node regulates the propagation delay to the atrioventricular bundle (or xe2x80x9cHISxe2x80x9d bundle). This coordination of the electrical activity of the heart causes atrial systole during ventricular diastole. This, in turn, improves the mechanical function of the heart. Atrial fibrillation occurs when anatomical obstacles in the heart disrupt the normally uniform propagation of electrical impulses in the atria. These anatomical obstacles (called xe2x80x9cconduction blocksxe2x80x9d) can cause the electrical impulse to degenerate into several circular wavelets that circulate about the obstacles. These wavelets, called xe2x80x9creentry circuits,xe2x80x9d disrupt the normally uniform activation of the left and right atria.
Because of a loss of atrioventricular synchrony, the people who suffer from atrial fibrillation and flutter also suffer the consequences of impaired hemodynamics and loss of cardiac efficiency. They are also at greater risk of stroke and other thromboembolic complications because of loss of effective contraction and atrial stasis.
Although pharmacological treatment is available for atrial fibrillation and flutter, the treatment is far from perfect. For example, certain antiarrhythmic drugs, like quinidine and procainamide, can reduce both the incidence and the duration of atrial fibrillation episodes. Yet, these drugs often fail to maintain sinus rhythm in the patient. Cardioactive drugs, like digitalis, Beta blockers, and calcium channel blockers, can also be given to control the ventricular response. However, many people are intolerant to such drugs. Anticoagulant therapy also combats thromboembolic complications, but does not eliminate them. Unfortunately, pharmacological remedies often do not remedy the subjective symptoms associated with an irregular heartbeat. They also do not restore cardiac hemodynamics to normal and remove the risk of thromboembolism.
Many believe that the only way to really treat all three detrimental results of atrial fibrillation and flutter is to actively interrupt all of the potential pathways for atrial reentry circuits.
One surgical method of treating atrial fibrillation by interrupting pathways for reentry circuits is the so-called xe2x80x9cmaze procedurexe2x80x9d which relies on a prescribed pattern of incisions to anatomically create a convoluted path, or maze, for electrical propagation within the left and right atria. The incisions direct the electrical impulse from the SA node along a specified route through all regions of both atria, causing uniform contraction required for normal atrial transport function. The incisions finally direct the impulse to the AV node to activate the ventricles, restoring normal atrioventricular synchrony. The incisions are also carefully placed to interrupt the conduction routes of the most common reentry circuits. The maze procedure has been found very effective in curing atrial fibrillation. However, the maze procedure is technically difficult to do. It also requires open heart surgery and is very expensive. Thus, despite its considerable clinical success, only a few maze procedures are done each year.
Maze-like procedures have also been developed utilizing catheters which can form lesions on the endocardium to effectively create a maze for electrical conduction in a predetermined path. Exemplary catheters are disclosed in commonly assigned U.S. Pat. No. 5,582,609. Typically, the lesions are formed by ablating tissue with an electrode carried by the catheter. Electromagnetic radio frequency (xe2x80x9cRFxe2x80x9d) energy applied by the electrode heats, and eventually kills (i.e. xe2x80x9cablatesxe2x80x9d), the tissue to form a lesion. During the ablation of soft tissue (i.e. tissue other than blood, bone and connective tissue), tissue coagulation occurs and it is the coagulation that kills the tissue. Thus, references to the ablation of soft tissue are necessarily references to soft tissue coagulation. xe2x80x9cTissue coagulationxe2x80x9d is the process of cross-linking proteins in tissue to cause the tissue to jell. In soft tissue, it is the fluid within the tissue cell membranes that jells to kill the cells, thereby killing the tissue.
Catheters used to create lesions (the lesions being 3 to 15 cm in length) typically include a relatively long and relatively flexible body portion that has an electrode on its distal end. The portion of the catheter body portion that is inserted into the patient is typically from 23 to 55 inches in length and there may be another 8 to 15 inches, including a handle, outside the patient. The proximal end of the catheter body is connected to the handle which includes steering controls. The length and flexibility of the catheter body allow the catheter to be inserted into a main vein or artery (typically the femoral artery), directed into the interior of the heart, and then manipulated such that the electrode contacts the tissue that is to be ablated. Fluoroscopic imaging is used to provide the physician with a visual indication of the location of the catheter.
Catheter-based soft tissue coagulation has proven to be a significant advance in the medical arts generally and in the treatment of cardiac conditions in particular. Nevertheless, the inventors herein have determined that catheter-based procedures are not appropriate in every situation and that conventional catheters are not capable of reliably forming all types of lesions. One lesion that has proven to be difficult to form with conventional catheters is the circumferential lesion that is used to isolate a pulmonary vein and cure ectopic atrial fibrillation. Lesions that isolate the pulmonary vein may be formed within the pulmonary vein itself or in the tissue surrounding the pulmonary vein. These circumferential lesions are formed by dragging a tip electrode around the pulmonary vein or by creating a group of interconnected curvilinear lesions one-by-one around the pulmonary vein. Such techniques have proven to be less than effective because they are slow and gaps of conductive tissue can remain after the procedure. It can also be difficult to achieve adequate tissue contact with conventional catheters.
Endocardial lesions to isolate pulmonary veins have also been formed as a secondary procedure during a primary open heart surgical procedure such as mitral valve replacement. A surgical soft tissue coagulation probe is used to form the endocardial lesions after the heart has been opened, either before or after the valve replacement. This technique does, however, increase the amount of time the patient is on pulmonary bypass, which can be undesirable.
Accordingly, the inventors herein have determined that a need exists for surgical methods and apparatus that can be used to create lesions around bodily structures and, in the context of the treatment of atrial fibrillation, around a pulmonary vein without increasing the amount of time that the patient is on pulmonary bypass.
Accordingly, the general object of the present inventions is to provide methods and apparatus that avoid, for practical purposes, the aforementioned problems. In particular, one object of the present inventions is to provide surgical methods and apparatus that can be used to create lesions around a pulmonary vein or other body structure in a more efficient manner than conventional apparatus. Another object of the present inventions is to provide surgical methods and apparatus that may be used to create lesions around a pulmonary vein without placing the patient on pulmonary bypass or increasing the amount of time that the patient is on pulmonary bypass when a related procedure is being performed. Still another object of the present inventions is to perform a diagnostic or therapeutic procedure, such as the coagulation of tissue around a body structure, without effecting collateral tissue that is not targeted for the procedure.
In order to accomplish some of these and other objectives, a surgical device in accordance with a present invention includes a relatively short outer member, a relatively short shaft located at least partially within the relatively short outer member and slidable relative to the relatively short outer member, and an operative element on the distal portion of the relatively short shaft. The distal portion of the relatively short shaft is adapted to be connected to the distal portion of the relatively short outer member such that the distal portion of the shaft member will form a loop.
In order to accomplish some of these and other objectives, a surgical device in accordance with a present invention includes a relatively short outer member, a relatively short shaft located at least partially within the relatively short outer member and slidable relative to the relatively short outer member, a control element defining a distal portion connected to the distal portion of the relatively short shaft and a proximal portion extending toward the proximal portion of the relatively short outer member, and an operative element on the distal portion of the relatively short shaft. The distal portion of the relatively short shaft may be used to form a loop.
In order to accomplish some of these and other objectives, a surgical device in accordance with a preferred embodiment of a present invention includes a relatively short shaft and a distal member having a flexible region and a malleable region and an operative element carried by the distal member. Preferably, the distal tip assembly may, if desired, also include a pull wire that facilitates the formation of a loop.
In order to accomplish some of these and other objectives, a clamp device in accordance with a preferred embodiment of a present invention includes first and second curved members and a tissue coagulation apparatus associated with the first and second curved members. The curved members and tissue coagulation apparatus preferably together define an open region that may be positioned around a body structure such as one or more pulmonary veins.
Such devices provide a number of advantages over the conventional devices used to create lesions around pulmonary veins. For example, the operative element carrying loops and the first and second curved members may be positioned around a pulmonary vein (or veins) on the epicardial surface in accordance with inventive methods disclosed herein. A continuous transmural lesion that will isolate the vein may then be created while the heart is beating. The heart need not be opened and pulmonary bypass is not required. As such, the present devices advantageously allow curative lesions to be formed around pulmonary veins without the difficulties associated with catheter-based procedures or the time on pulmonary bypass required by conventional surgical procedures.
In order to accomplish some of these and other objectives, a mask element for masking an operative element supported on a support body in accordance with a present invention includes a main body with a side wall defining an interior bore and a side wall opening. The mask element, which is preferably formed from thermally and electrically insulating material, is adapted to be positioned on the support structure such that a portion of the operative element is aligned with the side wall opening and a portion of the operative element is covered by the side wall. When the support structure is positioned with the side wall opening (and exposed portion of the operative element) facing the target tissue region, the remainder of the operative element will be covered by the side wall. As such, the present mask element protects non-target collateral tissue from being damaged, sensed or otherwise affected by the operative element.